The calculated severity for Plugins has been updated to use CVSS v3 by default. Plugins that do not have a CVSS v3 score will fall back to CVSS v2 for calculating severity. Severity display preferences can be toggled in the settings dropdown.
It is possible to identify the remote operating system by looking at certain files.
This plugin attempts to identify the operating system type and version by looking at certain files on the remote operating system (e.g., '/etc/redhat-release' on Red Hat).